Texture is black and won’t change
I had the same problem too, but I fixed it by following the instructions to this answer. Here are the steps:
1. In the Texture Paint tab, press N, and click Tool on the right side-bar.
2. Under Brushes click the X button to delete the brush, then add a new brush.
3. Then select a colour under Brush Settings, go to the Colour Picker dropdown, and then draw over the object.
I hope this works for you.